Not really a movie line but a scene from a movie.

In Star Wars: The Last Jedi. The scene where Leia gets blown out of the spaceship. She floats there a little then opens her eyes and proceeds to use the Force to fly through space towards the ship.

The audience absolutely erupted in laughter at that.

Titanic. Propeller guy.

I saw I am legend I cinemas with my brother I would have been 16 him 11.

When Will Smith killed his dog my brother started balling his eyes out and I started laughing at him uncontrollably. I'm sure from an outside perspective I looked like a psycho

I was a Radioman in the Navy, and some coworkers and I had gone to see Cider House Rules in the theater.

There's a scene where they come to inform someone that a plane with a loved one on board had been shot down.

To quote the movie:

When the plane was hit, the crew chief and the radioman jumped close together. The copilot jumped third.

We immediately started laughing when we heard that, because we were told that the Radiomen are some of the last to leave a sinking ship due to needing to destroy the cryptographic material. Hearing that a Radioman was one of the first to bail was too good to us..

The Titantic. In the scene when the dude falls off the back of the ship and hits the propeller on the way down. He hits it with a solid clang and someone in the theater loudly goes “oooooohh that’ll leave a mark…”

The entire theater fucking lost it.

The Samuel L Jackson scene in Deep Blue Sea, I know it's supposed to give the sense that nobody is safe, but it's so random and quick that it dives head first into comedy.

Not the movie that caused it, but during either the first or second Tobey McGuire Spider Man movie there is a scene where Peter tells Aunt May he is responsible for Uncle Ben’s death. Right during this dramatic scene in the theater a kid said pretty loudly (but not quite yelling) “I have to go poop!” Quite of a few of us burst out laughing during this heavy scene.

The parts from Jupiter Ascending between the start and the end.

Not a line, but I saw Matrix: Revolutions in theater on opening weekend. During the 1-on-1 fight with Smith in the rain, there's a slow-motion shot of Neo punching Smith in the face. It's such bad CGI the entire theater burst into laughter. I'm pretty sure it was intended to be dramatic, but after seeing the latest Matrix movie and how tongue-in-cheek it is about itself, I'm not entirely sure anymore.

In Before the Midnight, at the theater with my wife at the time, when the couple are at the hotel having a serious argument. I was losing it, laughing uncontrollably, because it mirrored my abusive relationship I was having with her so damn perfectly.

I'm not married anymore.

Not sure if this counts as it's not strictly a line but it's a family favourite story.

During Interview with the Vampire during a very tense scene, Tom Cruise walks out holding three severed heads by the hair. Well my sister started laughing hard, causing me and then the rest of the cinema to follow suit shortly after.

Not in the theatre but watching Kill Bill. Very tense moment when Uma Thurmam confronted the other woman (at 30 seconds https://youtu.be/sPfjd2bayVs). It zooms in on her eyes, plays the music, and I fucking lost it.

They used to do that in Bruce Lee movies and I was not expecting that in a Hollywood blockbuster. QT was inspired though.

Steven Seagal's death in Executive Decision was supposed be a dramatic moment instead the theatre I was in broke out in spontaneous clapping, laughing and cheering.

I watched the first hunger games movie in a Thai cinema. There is a scene where Katness (is that the main characters name...) breaks up with her boyfriend for some reason, neither of them is happy about it. The whole theater broke out in laughter, I have no clue why.

One of the Marvel movies, Avanegers I think?

"Get all of your spectrometers, put them on the roof and set them to detect gamma rays!"

Most of our group got a pretty good laugh out of that one in the theater.

Mark wahlberg in The Happening: “come on douchebag, think like a scientist”

All the emotional scenes of rebel moon part one . I know its a crime around here and reddit to like snyder but tbh i really like most of his movies like batman v superman series , army of the dead series , dawn of the dead etc they are by no means perfect but it is what it is and i like them for that .

But oh my fucking god the critics and haters were right on this one the emotional aspects of this movie were a riot and kora (or whatever her name was) just telling her backstory and making a terrible reason why its there etc made me wanna quit watching anyway i put myself through it mainly because of the time i spent to pirate it and hoping it would get good (it never did ) and no way in hell i'm watching the second part .

I saw revenge of the sith in the theater multiple times and there was no laughing at the no. I never noticed it being laughed at until the “do not want” translation gaffe.

You don't often hear people laugh out loud in a Finnish movie theater, so I remember the one time there was a sudden spontaneous burst. It was one of the Underworld movies where Bill Nighys character gets his head cut in half or something. I guess the visual was just so ludicrous and kind of mismatch to the tone that several people lost it at once.

https://www.youtube.com/watch?v=Fpr3l1jhK9Q&t=221s

😆

My friend and I saw Deep Impact in the theater, when the plan fails and the comet fragments are still going to hit earth, there is a dramatic moment when they explain to projected impact sites. One in the ocean and one ... in Canada. For whatever reason my friend and I both burst into laughter when they said Canada. The whole theater turned to glare at us.

It's been decades since I've been to the cinema, so I don't know if this counts, but a recent example I can think of is when I watched No Exit the other day, and laughed really hard both when one bad guy
::: spoiler spoiler
gets shot with a nail in the forehead by the other
::: and again when he then
::: spoiler spoiler
fell on his face and drove the nail home, literally
::: ¯\(ツ)/¯

I think James Cameron's "The Abyss" is kinda famous for having way more funny moments than intended.

I saw it in the cinema for its recent anniversary re-release. As you might expect most of the audience were enthusiasts and tended to lean older-male and slightly "technical" or "nerdy" in interests/professions. All to say that they were taking the film seriously. But then there were some, a minority, who didn't fall into that demographic at all. They found many moments in the film hilarious and were laughing out loud. Which rather annoyed the majority of the crowd some of whom would look around wondering where the annoying laughs were coming from. What's interesting is that over time the majority softened and started to find the humour themselves and laugh out loud at similar moments.

This is also mentioned in the wikipedia for the film ... it seems under the strain of making that movie some of the directing just got a little comical.

The Patriot (2000) dull Mel Gibson movie, as far as i can recall, anyway random dude gets head cleanly lopped off with a cannonball, buddies and i played too much UnrealTournament that day not to hear the "HEADSHOT" anouncer in our heads.

The only part of Oppenheimer I loved was when Oppie met Downey Jr.'s character. Oppie says, "You are a working man, I can respect that.

Downey: were you also a working man?

Oppie: no, but my father was.

I was the only person in the theater who laughed at this line and the people in front of me did not appreciate it.

In Alien: Resurrection I think, Ripley, goes on and on for most of the film about how she wants to exterminate aliens. My friends and I had been joking all film about how much like this one racist dipshit Ripley was in this film.

Then in a tense close up Ripley actually uses the dipshit's catchphrase: "I don't like it". So we bursts out laughing, annoying many other patrons.

You know how there are a lot of small theaters in Paris that screen old movies? There we were, watching a noir thriller classic "The Asphalt Jungle" one night.
As an epilogue, there's a tacked-on morality speech by a police chief, and you can smell the stench of The Hayes Code and J Edgar Hoover all over the goddamned thing.

Like a cheap piece of lazy propaganda. "Your local Police Department... tirelessly fighting day and night, to protect all regular citizens from society's external disruptive forces, like the Red Menace and Reefer Madness."

After being a rapt audience for the main story - which is a jewel of its' genre - this weird speech happens, it ends abruptly with a "The End" title card and we ambled out of the theater, that speech was the final disconcerting taste in our mouths, you could hear more than a few puzzled, snickering laughs.

I don't go to theaters enough to see entire audiences laughing, but I laughed..

I laughed uncontrollably at the climax/ending of Dark City at a friend's birthday party. It was his favorite movie at the time. He wasn't amused. I think the fact that he took the movie SO seriously, and that it ended in such an embarrassing schlocky way, was just too much for my poor system.

::: spoiler the ending spoiler It turns into a Dragonball-z fan film, with energy beams meeting in the middle and one guy straining and pushing harder and knocking the energy beam into the other, and other silly nonsense. It did not fit the tone of the movie AT ALL. Then, the movie ends as quickly as possible.

:::

Also laughed my way through most of the first Fast and the Furious movie, in the theater. At the time, it seemed like an amazing absurdist comedy, but these days it'd be very tamely dumb. Lots of people probably think of it as some sort of classic or some shit now.

Finally, nobody in the theater laughed once at Down Periscope. IMDB has it at 6.2, but.. nobody laughed. We walked out after giving up 30min in. edit: it was a different spoof movie from almost the same time that I'm thinking of, McHales Navy. Sorry for slandering you, Down Periscope, I'm sure you're amazing.

Not a line per se, but a scene. Watching The Haunting of Emily Rose in theaters and it's supposed to be a serious scene and maybe even shocking or scary. The possessed main character jumps out of a barn loft or house window... I lost my shit, laughed so loud. The way the girl jumped out was just too funny looking.

Not quite the same but having listened to the 1712 Overture several times before hearing the 1812, I didn't get some of the jokes until I actually heard the 1812, and THAT's when I laughed.

But on-topic me and the wife have been watching an animation film where the cinema was mostly kids and we got, and laughed out loud at, some of the "jokes for the grown-ups" that none of the kids did, who were all staring at us for laughing at something that was totally not funny for them.

I used to laugh during certain scenes in Commando. He'll do ridiculous things like rip the seat out of a truck like it's nothing.

I got lots of weird looks for laughing during multiple death scenes in the John wick movies, not sure if that counts...

I DID NAWT HIT HAR. I DID NAWT. OH HAI MARK!

The times that this has happened to me weren't serious moments that tickled me wrong, they were sophisticated references that only I got (or others were just quieter). I couldn't give you a specific example but it's happened at least twice.